The river rises south of Kirkby Stephen on the Cumbria /Yorkshire border and flows northwards to Carlisle before discharging to the Solway Firth. The eastern part of the catchment is drained by short, relatively steep streams from the Pennines; the western part includes tributaries of the Eamont system which arise in the eastern hills of the Lake District, and the major lakes, Ullswater and Haweswater. The catchment is largely rural, with farming the main industry. There are significant settlements on the upper part of the river at Kirkby Stephen and Appleby-in-Westmorland. Water quality in the upper reaches is classified as good and drinking water is abstracted to supply the city of Carlisle. The river is excellent for salmon (Salmo salar) fishing and also supports a sea trout (Salmo trutta) run. Many other species of fish are also found, eg brown trout (Salmo trutta fario), grayling (Thymallus thymallus), chub (Leuciscus cephalus), dace (Leuciscus leuciscus, eel, minnow (Phoxinus phoxinus), loach (Barbatula barbatula), river lamprey (Lampetra fluviatilis), sea lamprey (Petromygon marinus), and brook lamprey (Lampetra planeri), stickleback (Gasterosteus aculeatus) and bullhead (Cottus gobio). Otters and native crayfish (Austropotamobius pallipes) are also found in the Eden catchment. The Eden at Temple Sowerby is within the "River Eden and Tributaries" SSSI, and the proposed Special Area of Conservation (SAC) under the EC Habitats and Species Directive.

The sampling site is in an upland farming area at an altitude of about 100 m AOD. The surrounding countryside is hilly, with some woodlands, rising to the bare slopes of the Pennine hills to the east. These have been mined for lead and silver in historic times, and gypsum is still extracted. The underlying bedrock is Permo-Triassic Penrith Sandstone, with smaller tributaries of the Eden draining from the surrounding Carboniferous Limestone. The market town of Appleby, with a population of about 3 000, is roughly 14 km away by road. Its primary influence on the river is the discharge from the Sewage Treatment Works 16 km upstream, which currently has secondary treatment and, since January 1999, phosphorus stripping of the wastewaters it receives.

The ECN site is at the Eden Bridge in Temple Sowerby, at NGR 3604 5282, where the A66 trunk road crosses the river.

The catchment area is indicated with a black line.Click map to enlarge.